text: The pre-mRNA of this protein is subject to A to I RNA editing, which is catalyzed by a family of adenosine deaminases acting on RNA (ADARs) that specifically recognize adenosines within double-stranded regions of pre-mRNAs and deaminate them to inosine.  Inosines are recognised as guanosine by the cell's translational machinery.  There are three members of the ADAR family: ADARs 1-3, with ADAR 1 and ADAR 2 being the only enzymatically active members.  ADAR 3 is thought to have a regulatory role in the brain.  ADAR 1 and ADAR 2 are widely expressed in tissues while ADAR 3 is restricted to the brain. The double-stranded regions of RNA are formed  by base-pairing between residues in a region complementary to the region of the editing site. This complementary region is  usually found  in a  neighbouring intron but can also be located in an exonic sequence.  The region that pairs with the editing region is known as an Editing Complementary Sequence (ECS).